The present invention relates to an apparatus for varying the angle at which sheet stock is cut and, more particularly, to an adjustable device for varying the angle at which paper is supported relative to the back gauge and blade of a commercial paper cutter.
Images which vary in intensity from one location to another are printed by applying ink to a surface in a nonuniform manner. To do so, ink must be drawn at different rates from different points along an inking roller. This upsets the even distribution of ink on the inking roller and, in extreme cases, can temporarily reduce the supply of ink at some locations below that required for faithful reproduction of the image. The result is a localized reduction in image intensity, known as "ghosting", which can reduce or destroy the value of the finished product.
It is known that the problem of ghosting can be drastically reduced by tilting an image relative to the direction of paper travel in the printing process; however, the resulting page is difficult to cut on commerical paper cutters because borders of the image are oblique to the edges of the paper. Most commercial paper cutters are heavy instruments in which a thick stack of paper is held against a back gauge and cut by a blade parallel to the back gauge. An early cutter of this type is disclosed in U.S. Pat. No. 1,058,964 to Gray, Jr. Modern cutters are power driven and have back gauges movable automatically in a direction perpendicular to the blade, with the back gauge typically remaining parallel to the blade. Such machines are not easily adapted to vary the angle of cut from the built-in parallel condition in a controlled manner.
A technique commonly used to vary the angle of cut in machines of this type is to place a block of wood behind one end of a stack of paper and move the block until the paper is aligned. This method is crude, however, and requires manual realignment between successive cuts to the same stack of paper. Each cut must be aligned with a different set of marks a few thousandths of an inch wide.
Shears foro cutting paper and other forms of sheet stock have, in some cases, been provided with back gauge mechanisms capable of adjustment to vary the angle of cut. Such machines are disclosed in the following U.S. patents: U.S. Pat. No. 2,125,539 to Brownlee; U.S. Pat. No. 3,470,778 to Mohr; U.S. Pat. No. 4,033,572 to Cailloux; and, U.S. Pat. No. 4,577,538 to Hirata et al. Each of these mechanisms is rather complex, however, and the disclosed structures are not easily adapted to existing fixed angle machines.
Therefore, it is desirable in many applications to provide a simple and reliable apparatus for varying the angle at which a stack of paper is cut by a commercial paper cutter having a back gauge parallel to a cutting blade.